Background: The poor prognosis and public health burden of PTSD necessitates the development of more effective and broader treatment approaches. In the etiopathogenesis of PTSD, trauma memories become ingrained into key brain areas through conditioned learning and are triggered by various situations of daily life. The brain glutamate system plays a key role in the process of trauma learning and trauma memories via long-term potentiation. Ketamine administration modulates the glutamate system and has been used in the treatment of depression and PTSD. Previous studies demonstrate that a single low dose of ketamine rapidly improves symptoms of refractory PTSD and treatment resistant depression. Unfortunately the observed response is short-lived (4-7 days, maximum up to 2 weeks) and multiple doses often produce unacceptable side effects. TIMBER (Trauma Interventions using Mindfulness Based Extinction and Reconsolidation for trauma memory) psychotherapy, is a manualized and translational mindfulness based cognitive behavioral therapy specifically designed to target trauma memories and their expressions in PTSD patients. The placebo controlled pilot study examined the efficacy of a protocol combining a single infusion of low dose ketamine (0.5mg/kg) and TIMBER psychotherapy in subjects suffering from chronic PTSD. The objective of this pilot study was to optimize and individualize treatment of chronic PTSD using a rapid, effective, trauma specific, user friendly and inexpensive approach that uses cutting edge psychopharmacological combined with novel psychotherapeutic approaches.